1. Field of the Invention
The field of the invention relates to an improved tool holder useful in the storage battery manufacturing and assembly arts. It also has application in the dielectric testing art and as a holder of punches and dies in the plastics piercing art.
2. Description of the Prior Art
The prior art is best demonstrated by lead intercell connector and side terminal connector welders used in manufacturing storage battery supplied by, inter alia, Tiegel Manufacturing Company and the Taylor-Whitfield Company, and modifications thereof particularly as made by General Battery Corporation and the Prest-O-Lite Corporation, now both divisions of the Exide Battery Corporation. The Tiegel type welder jaws open and close around and weld together 2 storage battery intercell connectors which are to be welded on opposite sides of a cell partition by a toggle actuation means which bring a pair of the jaws holding welding electrodes toward each other. A problem presented by this apparatus is that the space between the electrodes in the jaws is fixed not only for a defined welding region but also the position of the battery case relative to the apparatus. These factors can cause either too much weld force to be applied to the weldment thereby generating too little heat when current is applied and an unacceptable melting of lead or not enough pressure which causes a defective weld. The GBC modification utilizes a single exteriorly mounted cylinder to drive the jaws which are disposed slidably on shafts opposite each other. However, the offset of the electrodes required by the battery application causes excessive wear on the bearings from rotation or roll about the shaft axis and binding or pitching along the shaft axis. Replacement life is often measured in a few months and wear causes severe misalignment of welding electrodes. Prest-O-Lite's modification of the Taylor Whitfield apparatus utilizes one exteriorly mounted cylinder on one jaw holder in the expectation that to do so would minimize wear problems. Roll is inhibited somewhat by the installation of exteriorly mounted roller stops which increase the friction load of the mechanism significantly. Pitch is not corrected at all. As a practical matter, the maintenance cycle is somewhat lengthened but not eliminated. Also the apparatus proves to be too bulky in practice to provide the flexibility necessary for robotic applications or to manufacture different battery configurations on the same battery line.
As an additional general problem, the jaw holders remain subjected to excessive torque because of uncontrolled welding pressure thereby causing the battery partitions molded into the case to become warped. As result there are unacceptable production losses occasioned by excessive down time for maintenance or electrode replacement.
None of the prior art improvements, because of their bulkiness are adaptable to robotic use, a present growing concern. In addition, a production line must accommodate an ever increasing number of storage battery designs. By locating cylinders around the jaws exteriorly the creation of truly flexible production lines is prevented.
The work piece, the polypropylene battery case and more particularly the partitions and the cast lead intercell connectors molded therein, are susceptible in the molding process to warpage, camber or thickness irregularity. The prior art teaches no economical way to weld, test or punch around, on or through the partitions given such susceptibility.
In addition, different welders have been required if welding side terminals instead of intercell connectors, thereby multiplying the number and types of equipment needed.